Conveyors using endless metal belts are well known. They offer reliable performance as well a high strength and endurance. Metal belts also offer the advantage of being easily cleaned and kept in a disinfected state, which is often an advantage or even a prerequisite, for example in connection to the conveying of food stuff and other products that require clean handling.
Prior art includes conveyors that comprise a metal belt carried by two opposite rolls that, in their turn, are supported by a framework. At least one of the rolls is displaceable in a direction from and towards the other roll in order to enable tensioning and release of the belt. The displaceable roll is carried by a carrier that is arranged so as to roll or slide along guides arranged on the framework. Typically the carrier is a sleigh or box that is supported by bearings which, in their turn, are arranged against guiding surfaces or in slots or grooves provided on opposite beams of the framework.
The beams that accommodate the bearings and along which the carrier is to slide during tensioning or release of the belt need to be stable and provide a well defined path for the bearings. If, for example, the beams are located only a little bit too far away from each other in the region in which the carrier is supported or are not held in position firmly and rigidly enough, there will be an enhanced risk of having a misalignment of the carrier, and the roll, in relation to the longitudinal direction of the conveyor. Such misalignment may be detrimental to the function of the conveyor and should be avoided. If, on the other hand, the distance between the beams in the region of the bearings is too small, there will be excessive resistance against sliding of the carrier. Accordingly, a well defined distance between the beams in the region in which they support the carrier and roll is a desired property of a conveyor.
Prior art solves this problem by suggesting frames that comprises frameworks that include a number of beams and cross bars that have as their task to confer stability to the beams that supports the carrier, thereby precisely determining their position in relation to each other, and to enable adoption of the tensioning forces that result from the tensioning of the belt. However, metal belt conveyors of prior tend to be rather heavy and bulky due to the often relatively complex and largely built framework. A less complicated and lighter frame design would therefore be appreciated. Frameworks of prior art also tend to adopt tensioning forces in a complex way. The tensioning force of the belt that acts in the longitudinal direction of the conveyor and the beams that carry the rolls, are adopted not only by said beams but by the whole framework. It would be desirable to design the frame of the conveyor such that as much as possible of that force would actually be adopted by said beams, thereby further reducing the necessity of further beams and cross bars and will add to the weight, size and complexity of the conveyor.
There is also a desire to enable the use of belts of different lengths in one and the same conveyor frame. In order to enable use of different belt lengths, the conveyor design must permit a corresponding displacement of the rolls to and from each other. It is a technical challenge to find design solutions that permit such displacement, and still promotes a compact and stable conveyor design.